The present invention relates to a suction member fixing apparatus for fixing phase-adjustable suction members for drawing and holding a trailing edge of a sheet which is gripped by grippers of a double-diameter cylinder and conveyed thereby to a cylinder body after phase adjustment in a sheet-fed printing press with a turn-over mechanism.
Along with a variety of printing operations, various types of sheet-fed presses with a turn-over mechanism, which can selectively perform single side printing or double side printing, have been proposed and are commercially available. Printing machines of this type are mainly classified into a single-cylinder type printing press comprising a double-diameter cylinder as a turn-over cylinder, and a three-cylinder type printing press comprising a transfer cylinder, a turn-over cylinder, and a double-diameter cylinder arranged therebetween.
FIGS. 3 and 4 are views showing arrangements of cylinders for explaining the printing operation of the three-cylinder type sheet-fed printing press with a turn-over mechanism. FIG. 3 shows a case of a single-side printing mode, and FIG. 4 shows a case of a double-side printing mode. The arrangement and operation of the printing press of this type will be described with reference to FIGS. 3 and 4. A blanket cylinder 1 is arranged below a plate cylinder (not shown) to be in contact therewith. An impression cylinder 5 is arranged obliquely below the blanked cylinder 1 so that its circumferential surface is in contact with the cylinder 1. The impression cylinder 5 has gripper units 4 each consisting of a gripper 2 and a gripper pad 3 in a gap formed in an outer peripheral portion of the impression cylinder 5. In a printing unit at the downstream side, a blanket cylinder 6 contacting a plate cylinder (not shown), and an impression cylinder 10 which has gripper units 9 each consisting of a gripper 7 and a gripper pad 8 and a circumferential surface contacting the blanket cylinder 6 are also arranged. A turn-over mechanism consisting of three rollers, i.e., a transfer cylinder 11, a double-diameter cylinder 12, and a turn-over cylinder 13, the circumferential surfaces of which are in contact with each other, is arranged between the two impression cylinders 5 and 10. Of these cylinders, the transfer cylinder 11 comprises gripper units 16 each consisting of a gripper 14 and a gripper pad 15 in a gap formed in an outer peripheral portion of the transfer cylinder 11. The double-diameter cylinder 12 has a diameter twice that of the transfer cylinder 11 and the like. Two sets of gripper units 19 and 20 each consisting of a gripper 17 and a gripper pad 18 are arranged at positions of equal angular intervals of the outer peripheral portion of the cylinder 12. In addition, two suction heads 21 and 22 as suction members are arranged at positions advancing from the grippers 19 and 20 by a predetermined angle in a rotational direction of the cylinder. A plurality of suction heads 21 and 22 are arranged on the outer peripheral portion of the double-diameter cylinder 12 along the axial direction, so as to be movable i the circumferential direction, so that a phase with respect to the gripper units 19 and 20 in the circumferential direction can be adjusted. Gripper units (A) 25 each consisting of a gripper 23 and gripper pad 24, and gripper units (B) 28 each consisting of a gripper 26 and a gripper pad 27 are arranged in gaps formed in the outer peripheral portion of the turn-over cylinder 13 to be adjacent to each other in the circumferential direction. The cylinders 1, 5, 11, 12, 13, 10 and 6 are driven and coupled by gears. A stationary gear fixed to a shaft and a pivotal gear can be alternately fixed to one end shaft of the turn-over cylinder 13. The stationary gear is meshed with the gear of the impression cylinder 10. The pivotal gear is meshed with the gear of the double-diameter cylinder.
With the above arrangement, in the case of the single side printing shown in FIG. 3, when the cylinders are rotated in the directions indicated by arrows, a sheet 30 which is fed from a paper sheet feeder and is gripped by the gripper units 4 of the impression cylinder 5 through swing pre-gripper units, is then gripped and conveyed by the gripper units 16 of the transfer cylinder 11. When the sheet 30 passes between the blanket cylinder 1 and the impression cylinder 5, an image of the first color is printed thereon. The sheet 30 is then gripped and conveyed by the gripper units 19 (or 20) of the double-diameter cylinder 12 from the gripper units 16 of the transfer cylinder 11. When the gripper units 19 face the gripper units (A) 25, as shown in FIG. 3, the sheet 30 is then gripped and conveyed by the gripper units (A) 25. Thereafter, the sheet 30 is gripped and conveyed by the gripper units 9 of the impression cylinder 10. When the sheet 30 passes between the blanket cylinder 6 and the impression cylinder 10, an image of the second color is printed on the same surface on which the image of the first color has been printed.
When the single side printing mode is switched to the double side printing mode, the pivotal gear is pivoted from a state wherein the gripper units 19 and 25 face each other in FIG. 3, so as to obtain a state wherein the suction heads 21 face the gripper units (B) 28, as shown in FIG. 4. Thus, the phase of the upstream-side cylinder group including the double-diameter cylinder 12 is adjusted with respect to the turn-over cylinder 13, and the phase of the gripper units 18 and 20 relative to the suction heads 21 and 22 on the double-diameter cylinder 12 is adjusted, thereby coping with a change in sheet size. Since the positions at which the gripper units 19 and 20 of the double-diameter cylinder 12 release the sheet 30 are changed by a length of the sheet 30 in the single and double side printing modes, an actuating position of a sheet release cam is adjusted. When the cylinders are rotated after the switching adjustment is performed in this manner, the sheet 30 subjected to printing on a front surface in the same manner as in the single side printing mode is conveyed while being gripped by the gripper units 19 (or 20) of the double-diameter cylinder 12 and drawn by suction at its end by the suction heads 21 (or 22). The sheet 30 is conveyed until its trailing edge reaches the contacting point between the cylinders 12 and 13, as indicated by numeral 30A in FIG. 4. In this case, the trailing edge of the sheet 30A is gripped upon opening/closing of the gripper units (B) 28 and suction/release of the suction heads 21, and is released from the gripper units 20 at the same time. Then, the sheet 30A is conveyed by the turn-over cylinder 13 while forwarding the trailing edge side. During conveyance, both the gripper units (A) 25 and (B) 28 are instantaneously opened/closed at different timings, and the sheet 30A is gripped by the gripper units (A) 25 from the gripper units 21 on the cylinder 12 and is conveyed thereby. When the gripper units (A) 25 face the gripper unit 9 of the impression cylinder 10, the sheet 30A is gripped by the gripper units 9, and is conveyed, as indicated by 30B in FIG. 4. When the sheet 30B passes between the blanket cylinder 6 and the impression cylinder 10, since its rear surface contacts the blanket cylinder 6, the rear surface is subjected to printing. In this manner, the sheet is subjected to the double side printing, and is delivered.
In the three-cylinder type sheet-fed printing press with the turn-over mechanism operated as described above, the gripper units 19 and 20 for gripping the leading edge of a sheet and the suction heads 21 and 22 for drawing the trailing edge of the sheet by suction are provided to the double-diameter cylinder 12, as described above. The phase in the circumferential direction of these members must be adjusted when the printing mode is switched from the singe side printing mode to the double-side printing mode or when the sheet size is changed. For this reason, various suction member phase adjusting apparatuses have been proposed. For example, a plurality of grooves extending in the circumferential direction are formed on the circumferential surface of the cylinder body to be parallel to the axial direction. The suction heads supported on the side of the cylinder body are inserted in the corresponding grooves by any means, and are moved in the circumferential direction along the grooves, thereby adjusting the phase. Thereafter, the heads are fixed.
However, such a conventional apparatus employs the following structure. More specifically, two arms are fixed to two end axial portions of a double-diameter cylinder supported by two side frames, and a plurality of suction members are fixed to a shaft coupling the arms. During phase adjustment, bolts for fixing the arms to the cylinder end shafts are loosened to perform phase adjustment. Thereafter, the bolts are tightened to fix the arms. In this structure, since the arms must be arranged inside the two side frames, the two bolts must be loosened and tightened in the narrow space defined by the frames each time the phase adjustment is performed. Therefore, a considerable labor and time are required for adjustment.